In some cases, a rocker shaft is provided therewithin with a lubricating oil passage for lubricating plural movable parts of an internal combustion engine, and this lubricating oil passage supplies oil pressure into a lash adjuster.
Also, in Japanese Laid-Open Patent Publication No. 2008-232078, the oil pressure is supplied into the lash adjuster through an oil passage exerting the oil pressure on a pin switching plural rocker arms between a coupling state and a non-coupling state. Related technologies are disclosed in Japanese Laid-Open Patent Publication Nos. 2009-264200 and 2010-275960.
For example, the oil pressure is supplied into the lash adjuster through a lubricating oil passage provided within a rocker shaft, which might cause a long period required for the oil pressure within the lubricating oil passage to increase and to reach a predetermined oil pressure, for example, in starting up the internal combustion engine, because of a comparatively low oil pressure within the lubricating oil passage. For this reason, the lash adjuster might not suitably act in starting up the internal combustion engine, which might cause a valve clearance to degrade noise and vibration.
Also, for example, as for the technology in Japanese Laid-Open Patent Publication No. 2008-232078, the plural rocker arms are switched between the coupling state and the non-coupling state by reducing the oil pressure exerting on the pin, which might also reduce the oil pressure within the lash adjuster. Accordingly, the lash adjuster might not suitably act, which might cause a valve clearance to degrade noise and vibration.